Update web_tests docs

Change-Id: I6065bfc40691995c463b6e30bc4b4b95ea174e63
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5321533
Commit-Queue: Alex Rudenko <[email protected]>
Auto-Submit: Alex Rudenko <[email protected]>
Commit-Queue: Philip Pfaffe <[email protected]>
Reviewed-by: Philip Pfaffe <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1265704}
diff --git a/docs/testing/web_tests.md b/docs/testing/web_tests.md
index fa0f400..db42db94 100644
--- a/docs/testing/web_tests.md
+++ b/docs/testing/web_tests.md
@@ -595,10 +595,10 @@
 
 * Do one of the following:
     * Option A) Run from the `chromium/src` folder:
-      `third_party/blink/tools/run_web_tests.py --additional-driver-flag='--remote-debugging-port=9222' --additional-driver-flag='--debug-devtools' --timeout-ms=6000000`
+      `third_party/blink/tools/run_web_tests.py --additional-driver-flag='--remote-debugging-port=9222' --additional-driver-flag='--remote-allow-origins=*' --additional-driver-flag='--debug-devtools' --timeout-ms=6000000`
     * Option B) If you need to debug an http/tests/inspector test, start httpd
       as described above. Then, run content_shell:
-      `out/Default/content_shell --remote-debugging-port=9222 --additional-driver-flag='--debug-devtools' --run-web-tests http://127.0.0.1:8000/path/to/test.html`
+      `out/Default/content_shell --remote-debugging-port=9222 --additional-driver-flag='--remote-allow-origins=*' --additional-driver-flag='--debug-devtools' --run-web-tests http://127.0.0.1:8000/path/to/test.html`
 * Open `http://localhost:9222` in a stable/beta/canary Chrome, click the single
   link to open the devtools with the test loaded.
 * In the loaded devtools, set any required breakpoints and execute `test()` in